The polyphenylene ether resins comprise a class of thermoplastic materials characterized by outstanding physical properties, a broad temperature use range and dimensional stability at elevated temperatures. They can be made by a variety of catalytic and non-catalytic processes from the corresponding phenols or reactive derivatives thereof. In general, they are prepared by the oxidative coupling of a phenolic compound with a complex copper catalyst. By way of illustration, descriptions of the preparation of polyphenylene ether resins are contained in Hay, U.S. Pat. Nos. 3,306,874 and 3,306,875 and in Stamatoff, U.S. Pat. Nos. 3,257,357 and 3,257,358, the disclosures of which are incorporated herein by reference.
In the Hay patents, polyphenylene ether resins are prepared by an oxidative coupling method comprising passing an oxygen-containing gas through a reaction solution of a phenol and a metal-amine complex catalyst. In the Stamatoff patents, polyphenylene ethers are prepared by reacting the corresponding phenolate ion with an initiator, e.g., an acid peroxide, in the presence of a complexing agent.
In Cizek, U.S. Pat. No. 3,383,435, incorporated herein by reference, it is disclosed that polyphenylene ethers and styrene resins are combinable in virtually all proportions to provide compositions having many properties improved over those of either of the components.
It has been proposed that compositions of polyphenylene ether resin and polystyrene can be modified by the inclusion of block copolymers of the vinyl aromatic compound, e.g., styrene, and a conjugated diene, e.g., butadiene. Such compositions, which have excellent impact resistance, are disclosed in U.S. Pat. No. 3,994,856. Compositions of a polyphenylene ether resin, a styrene resin and a block copolymer of an aromatic hydrocarbon such as styrene and a conjugated diene such as butadiene which has had its unsaturation reduced to less than 10% of its original value have also been proposed. These are disclosed in co-pending application Ser. No. 387,588, filed Aug. 13, 1973, now abandoned and assigned to the same assignee as herein.
It has not been discovered, quite unexpectedly, that using a combination of a block copolymer of the unsaturated type and a block copolymer of the saturated type will provide impact strengths better than using either one separately. This discovery permits important cost reductions in the hydrogenated block copolymer-based systems and improvement in melt flow in the unsaturated block copolymer systems, either one with improved impact properties. The new compositions can be modified with conventional thermoplastic additives, such as pigments, other flame-retardants, anti-oxidants, plasticizers, fillers, reinforcing glass fibers, and the like.